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Noctis Labyrinthus (NL) is located in the western part of the large extensional province of Valles Mariners and close to the vast volcanic plateau of Tharsis Montes. Within this area, linear pit-chains commonly occur in close vicinity to faults, inside the graben, and mainly connected to swarms of small cracks, generating a complex pattern of interconnected faults and a widespread grid of scalloped pit-chains. Such a striking spatial correlation between faults and pit-chains makes this area a location of interest to study the possible mechanisms of formation and evolution of these features. Previous work interpreted NL as a karst landscape with associated caves and water-related processes (Baioni et al.,2017; Weitz et al., 2016; Jackson et al.,2011; Thollot et al.,2010; Grindrod et Balme.,2010; Bérezi., 2008; Murchie et al.,2007; Johnston et al.,2006; Bibring et al.,2006; Boston.,2004;), a network of lava tubes (leone, 2014) or the result of volcano-tectonic activity (Mège et al, 2003, Schultz, 1998). In this work, we used the orthoimages H3210_0000 and H3221_0000 acquired by the High-Resolution Stereo Camera (HRSC) onboard Mars Express, bearing a resolution of 12.5 m/pixel, and for the surface topography, we utilized an individual Digital Elevation Model (DEM) from Mars Orbiter Laser Altimeter (MOLA) onboard Mars Global Surveyor, with a resolution of ~460 m/pixel. We have mapped all apparent faults and grabens within the selected area (N=3781). Each fault was traced by a single polyline or by a group of polylines when segmented, and we distinguished their size by assigning different colors, while the pit-chains were delimited by a polygon shapefile we performed a detailed analysis of the faults patterns and geometries over different lengths with the aim to provide a comprehensive model for the formation of the complex structural features in Noctis Labyrinthus. According to the occurrence of faults and pit-chains, a clear subdivision can be distinguished between the northern and the southern sectors of the studied area; The northern sector of Noctis Labyrinthus basically consists of smooth terrains, lacking troughs and pit-chains, while in the southern sector, pit-chains are well developed and mostly parallel to the ENE-WSW fault system. The azimuth distribution of fault populations shows two main trends in the rose diagrams: ENE-WSW and NS. The NS faults systems are apparently cross-cut by the ENE-WSW faults system, which seems to occur before pit chains formation. We infer a development of two fault systems potentially produced in response of bidirectional or radial extension, where distinct faults develop perpendicular to each extensional direction. The extension is driven by invariant regional stress field, in pure shear, where faults grow at different scales (Schultz et al., 2000; Turabi and Berg., 2011). We propose that a Synchronous or 2-Phase bidirectional regional extension can be the prime processes behind the formation of the rift systems in NL and the generation of T, L, and X-Shaped intersections between faults (Collanega et al., 2020). The presence of pit chains remains difficult to explain within this setting: the interaction with magmatic activity from the large nearby Syria Planum magmatic complex might have played a role in shaping these structures. In this scenario, dikes intruded below the graben floors might have exploited the local extensional setting creating dilatant conditions in correspondence of major structures. A subsequent pressure drop in the plumbing system might have led to a surface collapse forming the large pit chains. In conclusion, we hypothesize that the complex graben and pit chains system of NL is the combined result of the activity of a bidirectional extension likely in conjunction with the activity of a magmatic plumbing system.

SGI 2021

A Volcano-tectonic activity: possible scenario beyond the formation of the rift systems in Noctis Labyrinthus (Mars)

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L'Istituto Nazionale di Oceanografia e Geofisica Sperimentale - OGS e il Dipartimento di Matematica e Geoscienze dell'Università di Trieste sono orgogliosi di ospitare il 90° Congresso della Società Geologica Italiana a Trieste dal 14 al 16 settembre 2021. La modalità del congresso è interamente online.

Con il motto "Geologia senza frontiere" questo evento mira a promuovere le Scienze della Terra come disciplina scientifica proiettata nel futuro, oltre i confini geografici, politici e disciplinari, per comprendere meglio l'interno del Pianeta Terra e la struttura del sottosuolo, difendere la società da pericolosi eventi geologici, comprendere meglio la variabilità climatica, pianificare l'utilizzo delle georisorse in modo etico e nel rispetto dell'ambiente.


**Please note, times listed in the SCHEDULE tab (calendar icon) reflect YOUR LOCAL TIME ZONE. The main timezone for this conference will be Central European Summer Time.**

The National Institute of Oceanography and Experimental Geophysics - OGS and the Department of Mathematics and Geosciences of the University of Trieste are proud to host the 90th Congress of the Italian Geological Society in Trieste on 14-16 September 2021.  The Congress will be held entirely online.

With the motto "Geology Without Borders" this event aims to promote Earth Sciences as a scientific discipline projected into the future, beyond geographical, political and disciplinary boundaries, to better understand the interior of Planet Earth and the structure of the subsurface, defend society from dangerous geological events, better understand climatic variability, plan the use of geo-resources in an ethical way and respecting the environment.


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Earth Sciences should be understood not only as necessary for a better understanding of the interior of the planet Earth, but also as a defense of society from dangerous geological events, for the understanding of climatic variations, for the planning and use of georesources in a ethical and respecting and protecting the environment.

poster

Based on highly focused laser beams, optical tweezers are novel tools enabling contactless, non-invasive trapping and manipulation of particulate matter in different media including liquids, air and vacuum. Coupled with Raman spectrometers, optical tweezers allow high-resolution (i.e., no background noise from substrate) spectroscopic analysis of physico-chemical properties of dust grains.  Although in recent years they have been widely and successfully used in a variety of research fields (Jones et al.,2015), their application in space science is in its infancy (Alali et al., 2020, Polimeno et al., 2021). In principle, optical tweezers have key prerequisites for maximizing the scientific return from the analyses of planetary dust samples collected by the current and future sample return missions (e.g. Hayabusa-2, OSIRIS-Rex, Mars 2020; Chang’e 5), particularly during the preliminary investigation procedures in receiving/curatorial facilities (e.g. Smith et al., 2021). High-resolution, contactless and non-invasive analyses of planetary dust are actually expected to provide unprecedented information on the astrophysical origin and geologic evolution of their parent bodies. They are also expected to be instrumental for biohazard assessment for constrained sample return missions – like those targeting Mars or the icy bodies in the outer solar system, and the detection of past or extant extraterrestrial life. Optical tweezers, developed in our laboratories (Gillibert et al., 2019), were used to collect individual dust grains from powdered analogues and extraterrestrial materials (e.g. carbonaceous chondrites and lunar regolith; (Collareta et al., 2016) of known composition and to determine their composition and response to optical forces without substrate effects. Results document the high potential of this novel technique and will be used to assess its effectiveness in the micromanipulation and analysis of extraterrestrial dust from space sample return missions in receiving/curatorial facilities and its potential role within coordinated multiscale analytical protocols.

Optical Tweezers: Evaluating their analytical potential for space sample-return missions

This presentation set out with the aim of assessing the role of doubtful meteorites in the history of meteoritics. With respect to the research question, the presentation investigated the presumed witnessed fall that was recorded in Marsala (Sicily, Italy) on the night between 15 and 16 December 1834. Very little was found in the literature on this “extraordinary phenomenon,” and previous studies (e.g., Boguslawski, 1854; Grady, 2000) observed inconsistent results on whether the event was meteoritic in origin, because no meteorite fragments had ever been recovered. This explains why the Nomenclature Committee of the Meteoritical Society have classified this event as a doubtful meteorite, i.e., an object for which there was significant uncertainty over whether it was a real meteorite or, in some cases, whether it ever existed. The goal of this presentation is to contribute to the knowledge of the role of the doubtful meteorites in the history of meteoritics and to characterize the event that occurred in 1834 in Marsala. Thanks to the analysis of untapped sources, this presentation found that the event provoked a lively debate in the press and among the scholars of the time. Various Italian and foreign newspapers reported the news, while the pages of several Sicilian gazettes followed the scientific discussion about the real nature of the event. Even if doubtful meteorites have been discarded because they were not followed by the recovery of any meteorite samples and, in some cases, there is no certainty whether they really occurred, this research has found that their investigation may reveal unknown historical and scientific data. Although the current study is based on the analysis of a single doubtful meteorite, the findings revealed interesting aspects relative to the early stages of meteorite research, to the dissemination of science news, and to meteorite collecting over the centuries. Based on the results presented here, this presentation highlighted the role of doubtful meteorites as an important resource for the history of meteoritics and meteorite collecting as well as for studying the processes that have led to the scientific study of meteorites.

Tell me who you are. The study of doubtful meteorites in meteoritics and its history. A case study

The NASA’s MESSENGER mission reported that Mercury surface is mainly composed of basaltic lavas, with small areas composed of residual floating carbon phases due to a primordial magma ocean. In particular, compositional data obtained by X- and Gamma-ray spectrometers highlighted that basaltic lavas have unique characteristics among the differentiated planetary bodies (e.g., Solomon et al., 2018). Mercurian rocks appears to be extremely reduced, with very low Fe contents (< 2 wt.% Fe; with Fe/Si of ~0.06), an enrichment in Na and K, a wide variability of Mg and Ca, and a significant abundance of S (1.5-4 wt.%; e.g., Rothery et al., 2020). The composition of Mercury surface is so unique that we still do not have any terrestrial or extraterrestrial analogue. Only a few enstatite achondrites meteorites, the aubrites, have features that could, in part, resemble that of the Mercurian surface. Aubrites are primarily composed of large crystals of the Fe-poor, Mg-rich orthopyroxene (enstatite; En ~99). They also have minor phases of olivine, Ni-Fe-Si metal, and troilite, which indicate a magmatic formation under extremely reducing conditions. Recent works on MESSENGER-MDIS multispectral data suggested the presence of a few transitional elements such as Cr, Ti, Ni, and Co substituting Mg and/or Fe in pyroxenes (Lucchetti et al., 2018). Thus, to understand how the pyroxenes acquired such chemical abundances, and which magmatological meaning they have in the Mercurian magmatic system, we are acquiring Cr, Ti, Ni, and Co diffusion profiles in pyroxene in multiple aubrites (Pena Blanca Spring, Norton County, NWA 4537, NWA 6675). We are also planning to experimentally produce analog samples. Geochemical analyses will be performed using an EMPA system at the University of Milan and a LA-ICP-MS at the University of Pavia/CNR. This will allow us to: 1) better comprehend the formation and evolution of the Mercury crust; 2) derive spectral information from sample analogs in the range investigated by the SIMBIO-SYS/VIHI spectrometer on board the  BepiColombo mission before it reaches Mercury.

Evolution of Mercury-like lavas through aubrite meteorites: looking for sample analogs for the ESA/JAXA BepiColombo mission

Reflectance spectra properties are one of the most important information we can acquire from different bodies in the Solar System to classify them. A natural sampling of extraterrestrial material is represented by meteorites that can provide crucial information on the origin and evolution of their parent bodies. At present, sample return missions are one of the primary goals of the Solar System exploration.(e.g. Hayabusa 1 and 2; OSIRIS-REx). In particular, these missions are addressing asteroids formed by chondritic material, however among the minor bodies some have experienced process of differentiation and magmatic evolution and for these bodies the only sampling is provided by achondritic meteorites. These can span from primitive to highly differentiated and they are mainly composed of mafic minerals, feldspars and other minor compounds. These mineral phases can be investigated by VNIR spectroscopy to associate them to their parental bodies. In particular, within mafic minerals olivine is considered a paradox, as being a mineral forming the mantle of differentiated bodies, it would be expected to be present in a larger number of asteroids than it has been observed. Here we present preliminary spectroscopic results of a set of ungrouped achondrites (e.g. Al Huwaysah 010, NWA 5400, NWA 6704, NWA 6112, A 881548) with different amounts of olivine and variable Fe-Mg composition. These samples are studied by means of the VNIR reflectance spectroscopy to compare their spectra with available ones from literature. This procedure allowed us  to study the olivine composition in this spectral range and also the olivine amounts with respect the other main phases. From these samples we evidence how the olivine is clearly present in NWA 5400, Al Hawaysah 010, and NWA 6116. These meteorites are also the darker samples, with the first two samples showing a weak 2 mm band, indicative of the presence of pyroxene. The NWA 6704 and A 88548 are brighter and spectrally dominated by pyroxene, even if an asymmetry in the 1 mm band is present, suggesting the presence of olivine in lower abundance. These results are supported by detailed petrographic and mineralogical analysis of the selected samples. These achondrites are investigated both as powders and slab of rocks to show also the different effects due to the presence of a powdered regolith or a bedrock exposure. VNIR reflectance spectroscopy results will be also compared against possible parental bodies. Moreover, we characterized also the MidIR (i.e. 7-14 mm) range, where vibrational absorptions associated to the silicates are present. These analyses allowed us to detect mineralogical variation for these materials and they could be used as a  tool for future  planetary exploration of small bodies and planetary surfaces.

VNIR spectral properties of olivine bearing Ungrouped Achondrites

Geological maps have been historically a central part of the geological knowledge acquisition process: they are used to summarize all the relevant information of a site of interest and they provide a subdivision of an area into geological units. In its simplest form, a digital geological map produced in a Geographical Information System (GIS) typically takes the shape of a polygonal layer, which is needed to visualize the map. For this reason, it is quite common that mappers start new maps by populating a polygonal layer. Although this approach is easier to understand, it inherently has several drawbacks. In particular, the mapper will draw a contact twice for each neighboring polygon, resulting in the need of specialized topological editing tools. Furthermore, the contacts should be stylable (e.g., to represent how much certain we are about the contact). This is not possible with a polygonal representation alone and would require duplicating those contacts as an additional layer, which will, in turn, require additional editing whenever the map is updated. The solution to these issues requires adopting a different approach to avoiding data duplication inherent in a polygonal representation. We hereby present a python plugin for the popular QGIS software, which helps mappers adopt a more topologically-safe approach. Mappy expects its input to be constituted by lines, representing the geological contacts. Provided the lines intersect each other, these suffice to define the partitioning of the map in different units. To assign to each region additional information (i.e., unit’s names) a point layer, containing the needed attributes, is used. Mappy then takes care of updating a polygonal layer by generating the polygons and merging the attributes. This approach, similar to the one suggested by Skinner et al. (2018) has several benefits: any number of segments can be used to define a contact, making it possible to assign different attributes to different portions of the same line. The maps are easier to edit because any time a contact is modified the changes will automatically propagate to all affected polygons, without resorting to specialized topological editing tools. Furthermore, the contacts can be reused for map layout and directly styled. In this way, the mapper can draw the contacts working on just two units at a time, and the map can be progressively refined with no significant effort. These ideas can be implemented in any GIS of choice by performing a polygonization of the contacts and a spatial join of the points to assign the attributes, or Mappy can be used. Mappy enables the operator to adopt a polygons-free strategy during the whole creation of the map and provides the algorithms needed to re-generate the polygonal layer at any time. It also comprises additional tools for clipping the contacts at the intersection points and for automatic placement of the points. Once the base layers are crated (points and contacts) Mappy will update the resulting polygonal layer automatically, which style can be defined progressively during the creation of the map. Mappy has been already tested during the PLANMAP-GMAP mapping winter school, simplifying the generation of consistent geological maps to the students, and demonstrating the benefits of this approach, especially for newcomers which were able to produce new maps without the need of understanding complex topological editing tools. This tool will be further developed to support the upcoming mapping efforts during the JUICE mission, ESA ExoMars, and other missions interacting with the GMAP project.

Mappy: a python plugin to ease geological mapping with QGIS

In this work  we propose the geologic mapping of the Copernicus crater and the characterization of a potential landing site for a rover mission. Moreover, we have selected 68 scientific targets for in situ analyses and sampling, which can answer the ESA’s scientific questions about the history and geology of the Moon. Copernicus Crater is a relatively young impact complex crater, located on the near side and of about 100km indiameter. Studying Copernicus means having the possibility to get information about lunar crust, lunar interior, cratering process, and lunar explosive volcanism as well as constraining the age of a reference stratigraphic plane of the whole Moon, with an important impact on the dating system applied to the entire inner Solar System. Olivine spectral signature was detected (Liu F. et al., 2011), and this can provide information about the lunar crust and mantle. Absolute-dating Copernicus would improve the lunar chronological curve, used to date surfaces of all the bodies of the inner Solar System, through the crater size frequency distribution. Improving this curve means improving the age estimations of all these bodies. Moreover, this work can assist the foreseen human assisted robotic missions. As an incremental update of the work performed on Tusberti, (2019) we firstly performed a large-scale geological characterization and mapping of Copernicus crater, using remote sensing techniques, analyzing topographic, imaging and spectral data coming from Lunar Reconnaissance Orbiter (LRO), Selenological and Engineering Explorer (SELENE), and Clementine missions where many interesting features were visible (like cinder cones, vents, melt differentiated, fresh craters and presence of olivine). Therefore, we generated two geological maps, one covering the entire Copernicus crater (at a scale of 1:400000) and one focused on its NW quadrant (scale 1:100000). In fact, by analyzing the topography in terms of slope and roughness we infer that this quadrant could be the best candidate for the landing area. Based on those elaborations and on a preliminary hazard study (following the constraints from Pajola M. et al., 2017), we selected a tentative landing ellipse with in mind the engineering constraints of the now deprecated HERACLES mission and the forthcoming EL3 (European Large Lunar Lander). Moreover, the landing ellipse was selected not only for safety reasons but also because 68 potential sampling sites which are located in reachable areas. These sampling sites are carefully selected in order to fulfill the major ESA questions related to Moon exploration. 

Geologic mapping and landing site characterization in Copernicus Crater (Moon)

Rembrandt, a 715 km-diameter basin on Mercury centered at 32.89°S,  87.86°E, constitutes a remarkable example of the stratigraphic variability on Mercury. The uppermost smooth plains of volcanic origin, which are temporally unrelated to the impact event, have been distinguished by the surrounding smooth plains utilizing spectral information. Moreover, it is crosscut by a prominent thrust system more than 1000 km long with NE-SW orientation. This consists of a set of lobate scarps and wrinkle ridges with inverse to transpressional kinematics (Massironi et al., 2015) and is named Enterprise Rupes (Ferrari et al., 2015; Galluzzi et al., 2015; Semenzato et al., 2020). Its formation is attributed mainly to crustal shortening induced by global contraction (see Semenzato et al., 2020 and references therein). The aim of this work, as part of the PLANMAP Horizon 2020 project, is to use all the available geologic information to provide a comprehensive 3D model of both the structural setting and the thicknesses of the main units of the Rembrandt basin infilling using explicit modeling approach.  While implicit modelling and its effectiveness rely on the amount of available data both on the surface and the subsurface to provide a best-fit solution that satisfies all the constraints, the explicit geological modelling implies a more extended geologic interpretation based on the available data, which is also subject to the operator’s experience. In practical terms, this modeling approach is essentially based on the construction of several interpreted parallel and intersecting cross-sections that are then interpolated generating mesh surfaces. The advantage is that it can be applied in areas with low amount of data, especially with few subsurface constraints. We mainly based our reconstruction on the geo-stratigraphic map and geologic cross-section of Rembrandt basin from Semenzato et al. (2020). Additional constraints, regarding fault kinematics and fault plane geometry were derived by Galluzzi et al. (2015) and Crane (2020). As a basemap, we used the MESSENGER MDIS global mosaic at 166 m/pixel together with the MDIS global DEM (665 m/pixel). The base unit of Rembrandt (named IT - para-autoctonous intracrater plains) is overlaid by two different events of infilling: the YIP (Young Interior smooth Plains) and OIP (Older Interior smooth Plains) units. Their thickness was estimated in Semenzato et al., (2020),and among the methods one implies the presence of impact craters excavating and exposing the inner basin stratigraphy. We also used such craters for the construction of the interpreted cross-sections in complement to the one presented in that work. We built 14 cross sections that were subdivided into two intersecting sub-parallel sets. The interpreted subsurface horizons were used for mesh interpolation together with the geologic contacts between the different units on the surface creating meshes representin ghte top of the YIP, OIP and IT basin infilling units. The volume between them was then calculated by means of a tetrahedral mesh. The structural modelling was performed by means of the structural mapping from Semenzato et al., (2020) and Ferrari et al., (2015). The faults’ vergence and their angles were extracted thanks to the illumination conditions on the image mosaic and topography, and also to the measurements provided by Galluzzi et al., (2015) on displaced impact craters, to the work by Crane (2020) and Massironi et al., (2015). The Enterprise rupes thrust geometry was constructed including its splays and backthrusts, as well as the contractional lobate scarps and extensional radial features within the basin units. Also in planetary geology and with relative scarcity of data, the 3D geomodelling proves to be a useful tool in order to check surface interpretations and mapping, that might improve or change once reconstructed in 3D and helps also to refine volume calculations and the shape of geoogic bodies. Further work will focus on forward and backwards modeling of the Enterprise Rupes system deformation.

3D geo-model of Rembrandt basin on Mercury: structural framework and infilling 

Phosphorus is ubiquitous in planet Earth and plays a fundamental role in all living systems. Finding a reasonable prebiotic source of phosphorus is not trivial, as common sources where it is present nowadays are in the form of phosphate minerals, which are rather insoluble and non-reactive materials, and, accordingly, unavailable for being readily incorporated in living organisms [1]. A possible source of phosphorus is from the exogenous meteoritic bombardment and, in particular, in iron/nickel phosphides [3,4,5]. These materials, by simple interaction with water, produce oxygenated phosphorus compounds, which can easily react with organic molecules, thus forming C-O-P bonds [6,7]. It has been estimated that up to 10% of the early Earth crust was composed by phosphide minerals, after the heavy meteor bombardment, and that many tons per year of phosphorus oxygenated compounds have been produced [8]. In the present work, periodic ab-initio simulations at PBE level (inclusive of dispersive interactions) have been carried out on Fe2NiP-schreibersite, as a relative abundant component of metallic meteorites, in order to characterize structural, energetics and vibrational properties of both bulk and surfaces of this material [9]. Moreover, also the interaction with water was analyzed, modelling both high and low coverage regimes, in order to study the corrosion process which ultimately leads to the production of phosphorus oxygenated compounds, like phosphites (HPO32-/H2PO3-) and phosphates (HPO42-/H2PO4-).

Ab-initio modelling of Fe2NiP-H2O interaction: a phosphate factory for Early Earth

There has been no other mission or mission program that has more fundamentally changed our way of understanding space than the Apollo Lunar Exploration Program. The first human landing on an extraterrestrial body, the first in-situ study by a trained geologist. The first sample return, the first extraterrestrial seismic experiment and network, the first extraterrestrial heat flow measurement, and dozens of surface experiments, to name a few. Project Apollo landed six lunar modules and twelve astronauts on the Moon between July 1969 and December 1972 to explore and undertake scientific exploration traverses. It returned 382 kg of lunar samples and a wealth of data that are still intensely explored today. As examples we note that only a few years ago application of modern seismic data analysis tools to the historic Apollo seismograms have revealed what are arguably reflections of waves from the lunar core. Moreover, traces of water have recently been found in re-analysis of lunar samples.  In this presentation we will discuss how the scientific input and science and engineering synergism during the Apollo Lunar Exploration Program resulted in ever-increasing capabilities to visit a wide range of landing sites on the Moon and to conduct geological traverses that culminated in the Apollo 15-16-17 Scientific Expeditions to the  Moon.  Each succeeding Apollo mission was characterized by increasing exploration capabilities (landing accuracy, stay time, EVAs, mobility, experiments, tools, etc.). We present a brief review of the landing sites, surface operations and science return of each succeeding Apollo mission and show how science and engineering synergism resulted in a rapid transition from achieving a national goal (Apollo 11) to sophisticated scientific expeditions targeted to areas critical to understanding the origin and evolution of the Moon.  The Apollo Exploration program resulted in an entirely new paradigm for the origin and evolution of the Moon, and indeed, other planets. Lessons for future human and robotic exploration, including NASA’s Artemis Program, will be described.

The Apollo Lunar Exploration Program: how Increasing Science Capabilities Resulted in a Revolutionary New View of the Moon

Multidisciplinary efforts are currently boosted by an urgent need to improve our understanding of Earth’s lava systems in sight of their future exploration on other rocky bodies of the Solar System. Among the many structures documented in lava fields, lava tubes are one of the most enigmatic. They constitute a peculiar type of caves dug by molten lava flows. These roofed conducts are very efficient thermal structures enabling channelizing lava transport over long distances. The longest lava tubes are found on volcanic plateau characterised by a gentle slope (<2°) or on volcanic islands (e.g. Hawai’i, Canaries, Iceland, etc.). These structures are easily recognizable from the surface by skylights and collapses on the roof forming pits chains, which allow the reconstruction of the tube path. Due to the similar characteristics of basaltic volcanism on other rocky bodies (e.g. Mars and the Moon), it is expected that lava tubes have similar origins and morphologies to those on Earth. Indeed, analogous conformations of aligned collapses have been seen on the surfaces of Mars and the Moon (Haruyama et al., 2012). This discovery has led to a growing interest as these structures could be suitable sites for future exploration and/or permanent human settlement. Located in the north-eastern part of the island of Lanzarote (Canary Islands), the La Corona lava tube system with its 7.6 km of total length (~8.9 km of cave development) and 10-20 m diameter is one of the terrestrial largest volcanic cave complexes. Accordingly, to the particular geological context in which it arose, La Corona system is one of the most studied. Indeed, the Canarian archipelago represents both long-term and spatially focused volcanic activity over a poorly mobile tectonic plate [less than ~2 cm/yr, during the last 30 Ma (Gaina et al., 2013)]. This environment identifies the Canaries as one of the best analogues of the Martian one-shell plate volcanism on Earth (Meyzen et al., 2015). What makes this inflated lava tube so interesting is a pyroclastic layer, derived by the initial Strombolian activity of La Corona vent (Carracedo et al., 2013) and interleaved within the lava flows crossed by the tube. The layer follows the tube for at least one-third of its extent and we speculate that it could have been pivotal for the inception of the inflation process. By analogy, similar geological settings could be favourable for the formation of lava tubes on rocky bodies like Mars and the Moon, where weak layers of pyroclastic deposits or fine regolith are thought to be common.

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Optical Tweezers: Evaluating their analytical potential for space sample-return missions

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